This invention relates to an electrode for secondary battery having high capacity and excellent in charging and discharging characteristics. More specifically, it relates to a flexible electrode for alkali metal secondary battery which can constitute a cylindrical secondary battery as a coil-shaped electrode or a sheet-shaped secondary battery as a thin sheet-shaped electrode.
As the electrode for lithium secondary battery, it has been proposed to use an electroconductive polymer such as polyacetylene. However, an electroconductive polymer is insufficient in the doping amount of lithium ions, i.e. electrode capacity and stable charging and discharging characteristics.
Also, an attempt has been made to use lithium metal as the negative electrode of lithium secondary battery, but in this case, the charging and discharging cycle characteristics are extremely poor.
More specifically, during discharging of the battery, lithium moves as lithium ions from the negative electrode body into an electrolyte, while during charging, the lithium ions are again electrodeposited as metallic lithium onto the negative electrode. By repeating such charging and discharging cycle, the metallic lithium electrodeposited by accompaniment with such cycle becomes shaped in dendrite. Since the dendrite-shaped metallic lithium is a very active substance, it decomposes the electrolyte, thereby causing an inconvenience to occur that the charging and discharging cycle characteristics of the battery are deteriorated. Further, when this grows, the dendrite-shaped metallic lithium electrodeposited product finally reaches the positive electrode penetrating the separator, there ensues the problem of causing short-circuit phenomenon to occur. In other words, there ensues the problem that the charging and discharging cycle life is short.
For avoiding such problems, it has been attempted to constitute a negative electrode by using a carbonaceous material prepared by sintering an organic compound as a carrier material on which an alkali metal, particularly lithium is carried as the active substance. By using such negative electrode, the charging and discharging characteristics of the negative electrode could be dramatically improved. But on the other hand, an electrode molding material by use of this carbonaceous material as a carrier is poor in flexibility, and no satisfactory electrode shaped in sheet or coil could be obtained.